Atkins Godmanchester flood risk management scheme

Atkins was the design consultant and CDM-Coordinator on this award winning flood risk management scheme.

Situated on the River Great Ouse in Cambridgeshire, the small town of Godmanchester is steeped in Saxon and Roman history. After widespread flooding in 1998, the Environment Agency secured £10m to construct flood defences to protect the town over the next 100 years.

This challenging scheme has reduced the risk of flooding to over 556 properties in the town. The 1.5km of flood defences pass through a conservation area including 31 gardens of riverside properties, many of which are Grade ll listed. The town also lies adjacent to Portholme Meadow, Europe’s largest area of natural wet meadow and a designated Special Area of Conservation (SAC). It is also a Site of Special Scientific Interest (SSSI) for the grassland communities it supports. Dialogue with local residents, councils and other third parties has been ongoing since the initial study in 2005.

As well as the 1.5km of flood defences, the scheme included river widening and dredging around the Cooks Bridge crossing to improve conveyance, and two pumping stations to control seepage through the underlying soils.

The flood defences tie into the A14 embankment which runs across the floodplain to the northeast of the town. The defences, ranging in height from 0.4m to 1.8m, are a mixture of walls and embankments in public realm areas, private gardens and open fields.

A suite of environmental mitigation measures were also implemented. Mature trees and planted areas were retained where possible, and tree protection fencing was erected. Ecology surveys identified Great Crested Newts within a nature reserve pond, and during construction, one Great Crested Newt found within the working area was successfully relocated by a licensed ecologist to the pond outside the site.

Nesting birds and waterfowl are a regular feature of Godmanchester. Swans use the causeway in the centre of town, which is also an important fish spawning habitat. All vegetation and tree removal activities were undertaken outside of the nesting bird season. However, nesting ducks and birds were encountered within the working areas. By ensuring access routes to and from active nests, viability of the nests was managed whilst maintaining the overall construction programme.

Excellent teamwork was at the heart of this project’s success. They minimised the impact of the scheme on the area’s character while developing a solution that was embraced by landowners, the client, local planning authority and funding partners. In recognition of their success, the team received the highest Environment Agency award for health and safety management, as well as the Outstanding Contribution Award at the 2014 BCI Awards.